We begin with the work of Bazalgette in inventing and installing the first sewer system underneath London. In his times, there were severe outbreaks of Cholera, and the scientific explanations for the nature of the disease and its spread was a matter of controversy. Some believed it was an airborne disease, and others believed it was a bacterial plague which was spread by the filthy water. Bazalgette, under great opposition from city planners and councils, managed to develop a design of drainage which would carry the city's sewer and rainwater away to the sea, using underground brick passageways and enormous pumps.
![Image](https://hepburnsays.files.wordpress.com/2016/03/sir-j.jpg?w=225)
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John Snow was instrumental in gathering and mapping the data on disease cases in London, and he was able to trace the epicenter to a water pump in a certain neighborhood.
http://johnsnowbicentenary.lshtm.ac.uk/about-john-snow/
Both of these men, against expert advice and opinion, managed to prove that the disease was spread by bacteria in water, and in some foods. (Georges Cuvier died of cholera which he contracted from cream.) Today, we can be thankful for the dedicated engineers and laymen who pursued this scientific problem to its conclusion, and which spares us from the worst diseases and epidemics through the responsible planning of our wastewater treatment and also through food processing which kills viuses and bacterium.
I hope this adds to the discussion when considering the explanations for the deadly disease epidemics and pandemics in history, and that future generations can feel gratitude and admiration for the people from all walks of life, such as Joseph Bazalgette and John Snow, who solved these enormous problems through their work and inventions. And we also may feel some appreciation for the English-speaking nations which were free enough for these inventors to study and pursue their ideas, and bring them into being.